Field effect transistors, such as a MOSFET disclosed in JP-A-2000-294777, have a channel formed on the surface of a SiC substrate. JP-A-2000-294777 discloses an approach for providing these devices with high carrier mobility and excellent device characteristics. According to this approach, a flat portion between bunching steps occurring in a high-temperature annealing process for the substrate is used as a channel portion for the field effect transistor. Also, it is designed to have a channel direction in which the moving direction of carriers in the channel does not cross the bunching steps.
However, JP-A-2000-294777 fails to disclose an approach for achieving practical applications with respect to the interface between the SiC substrate and a gate insulating film.